Distillation of olefin-hydrogen chloride mixtures



' Patented June v7, 1949 .UNITED STATES PATENT OFFICE 2,472,610 DISTILLATION F OLEFIN-HYDROGEN. CHLORIDE MIXTURES Alan C. Nixon, Berkeley, David C. Lehwalder,

Oakland, and Harry A. Cheney, Berkeley, Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application November 17, 1947,

. Serial No. 786,544

- tures comprising hydrogen chloride and propylene by fractioning means.

Mixtures comprising hydrogen halide in admixture with oleflnic hydrocarbons generally constitute a considerable proportion of the materials separated from the reaction products obtained in processes involving the interaction of oleflnic hydrocarbons with a halogen or a halogen halide or the treatment of olefinic hydrocarbons in thepresence of a halogen or a halogen'halide. In processes such as, for example,- those wherein an oleflnic hydrocarbon reacts with, or is treated in the presence of, chlorine or hydrogen chloride, or organic halides are subjected to catalytic or thermal decomposition, mixtures comprising unconverted charge material or reaction products consisting essentially of hydrogen chloride and olefinic hydrocarbons are generally obtained in the product separating zone of the system in such quantities that the practicability of the operation is often dependent upon the eflicient recovery of the components of these mixtures in a condition suitable for further utilization. Thus in the chlorination of a normally-gaseous hydrocarbon such as, for example, propylene, there is obtained a mixture consisting essentially of propylene and hydrogen chloride in considerable amount. Methods heretofore employed to effect the recovery of the substantial quantities of hydrogen chloride thus produced comprise such methods as the contacting of the mixture with water thereby recovering the hydrogen chloride as aqueous hydrogen chloride. Many of the processes employing hydrogen chloride as a reactant or treating material necessitate its utilization in the anhydrous or substantially anhydrous state, however. Recovery of the hydrogen chloride by methods involving its contact with .substantial amounts of water therefore necessitate the additional complex and costly steps of dehydrating the aqueous product. Methods enabling the emcient separation of the hydrogen chloride from admixture with olefinic hydrocarbons in anhydrous or substantially anhydrous condition are therefore not only desirable but are often essential to bring the processes in which the mixture comprising it is produced within the realm of practicability.

Separation of the hydrogen halide by large scale fractionating means has heretofore gener- 8 Claims. ((1202-57) ally been impractical because of the relative ease 1 with which the olefinic hydrocarbon combines with the hydrogen halide under fractionating conditions employed resulting in the formation of addition products of the hydrogen halide and the olefinic hydrocarbon. Thisis particularly'the case when fractionation is carried out at the relatively high pressures which must be resorted to. in order to obtain overhead product consisting essentially only of hydrogen halide from mixtures comprising the hydrogen halidein admixture with a normally gaseous olefin such as, for example, propylene. The following example is illustrative of the relative ease with which a hydrogen halide and a normally gaseous olefin will undergo the addition reaction under fractionating conditions of relatively elevated pressure in a column wherein the mixture undergoing fractionation is in contact with a steel surface such as that generally found in practical scale fractionating equipment.

Etample I A propylene-hydrogen chloride mixture is subjected to fractionation in a steel column containing a packing of 0.5 inch mild steel rings. Operating conditions employed, conversion of hydrogen chloride and rate of isopropyl chloride production encountered within the column are indicated in the following table:

Distillation pressure lbs/sq. in./gauge....- 1'15 Top temperature C -25 Reboiler temperature "C 30 Total feed rate lbs/hr 120 K01 content of feed, mol per cent 15 Water in feed-parts per million to 200 Duration-hrs 2'1 isopropyl chloride production rate lbs/hr.-- 13 HCl conversion, per cent..-

This represents an overall production .of isopropyl chloride of approximately 44 lbs. per 1000 sq. ft. of steel surface per hour.

It is apparent from the foregoing example that the considerable loss of material charged to the fractionating column occasioned by its conversion to isopropyl chloride renders impractical recourse to such an expedient for recovering the components of the hydrogen chloride-propylene mixture. The impracticality of the method is further evidenced by the rapid increase in the rate of the addition reaction'with increase of temperature under such fractionating conditions. Thus the execution of the above fractionation at a column temperature of only about 10 C. higher than that of the; example, occasioned by the use pounds, results in a threefold increase in the rate of isopropyl chloride production.

Although the interaction of hydrogen halide and the olefin proceeds at a relatively low rate hen the fractionation is effected in glass apparatus, such material is obviously not suited as a material of construction for equipment to be used in practical scale operation. It has now been the propylene in contrast to the effect exerted by the surfaces of the materials of construction compared therewith, but it indicates the inability of found. however, that a hydrogen halide, such as 5 deducing such qu lity from that which is known hydrogen chloride, can be separated efllciently of the relative behavior of this material and the from mixtures comprising it in admixture with materials compared therewith as catalysts, antia normally gaseous olefin such as, for example, corrosion materials. et e h degree of propylene, by fractionation on a practical scale efllcieney with which hy ro en chloride may be when the fractionation is eifected in a fractionat- Separated on a practical scale from a normally ing zone wherein substantially all surfaces in gaseous olefin admixed therewith in accordance contact with the mixture undergoing fractionawi h the invention by fractionating such mixture tion consist essentially of nickel. It has been v in a fractionat zone aflording contact of subfound that the utilization of a fractionating zone n fllly only nickel surfaces with the material affording a contact of substantially only a nickel undergoing fractionation is illustrated by the folsurface with the materials undergoing fractionawing example: tion enables the utilization of the high pressures x ple 1 1 and corresponding relatively high temperatures t n ti of a propylene-hydrogen chlonecessary to the attainment of an overhead conride mixture containing approximately 28 per slstmg essentially only of hydmgen halide with cent by weight of hydrogen chloride in a 40 plate. the loss of only a relatively minor amount of the nlckebclad incl-donating column at a pressure of materials charged due to interaction of the 225 lbs. results in an overhead product consist- .ponents thereof within the fractionating zone. essentially of 99 25% by weight f hydrogen The exceedingly low rate of reaction of hydrochloride and bottoms containing 97% by weight gen chloride and propylene in the liquid phase in of propylene and40 35% by weight of isopropyl the presence of nickel as compared to that unchloride. About 750 per day of isopropyl avoidably ed in the presence of a Surface 0f chloride is produced representing a conversion of readily available materials of construction other hydrogen chloride to isopropyl chloride of t n ni l is vi n y the following Execution of the fractionation in a fractionation p e column presenting a surface of mild steel to the Example II material undergoing fractionation under other- 300 glass vessels are immersed in an ice wise substantially identical conditions results in bath and connected to a pressure gauge the prOdllCtlOIl .Of about lbs. or isopropy] proximately equal quantities r HC1 and Dropy]. chloride per day, representing a conversion of ene are charged to the vessels, filling about 80% hydmgen chloride to lsoplopyl'cmoride 0 of their total v01ume The fi t of Various Utilization of a fractionating column wherein the terial of construction upon the reaction rate of Surface in Contact the material undergoing the hydrogen chloride-propylen additi fractionation is nickel reduces the undesired isotion is obtained by placinga suitable quantity of P w chloride production to y about /=w o construction material in each of the vessels below 4 that obtained in a s l l n under o er e the surface of the liquid therein. The rate of Substantially identical conditionsreaction of o and propylene is found by In the execution of the invention the presence te -mining the amount of reaction products of any Substantial amount Of Water in the hydroformed and by noting the rate of decrease of the s halide-olefin mixture charged o he fracpressure in the vesse1 w the Second method tionating zone is preferably avoided. If necessary it is observed that when the reciprocal of absothe-mixture to be fractionated may be subjected lute pressure is plotted against time, t points to suitable dehydrating means to remove at least fall along a straight line. The slope of this line the greater amount of any Water contained 1 a measure of the reaction rate therein prior to its passage to the fractionating In the following table are indicated for each Zone- Suitable dehydrating ea s compr se any test, the nature and surface area of construction of the available conventional d y methods s, material tested, the initial HCl concentration, the for examp e, the passage of the mixture throu h duration of the test, the amount of isopropyl bed f a suitable at g a ent such as chloride formed in per cent of total charge. and dso ptive u i calcium chloride, calcium th t of reaction of HC] and propylene l t sulfateor the like. It has been found, however, to the rate in the presence of glas alone, that though the presence of any substantial Reaction ,3? Surface Present 328; 5% L ltigggagl fi gla i i r Sq. In. um sq. in'oi" per cent per cent surface Glass 45 32.4 17.2 4 1 .do 185 baa 22 25 1 icke] 7 45.2 19 12 a ShlinleSH stee 7 44s 19.5 to -monel 6 49. 3 46 58 llfi Low Carbon SteeL. 6 46. 2 l9. 6 35 180 on r 7 4H 48 85 230 'Fnrfnml K ll-bate 1 7 E3. 3 l8 300 Rusty Tron... 37 55.4 17 83 475 Ferric Chloride. (1% by 35.5 48 96 weight) I Graphite base with iuri'ural resin hinder.

Not only does the foregoing example evidence the unusual degree to which the nickel surface amount of water in the feed to the fractionating zone is to be avoided, the removal of substantially possesses the quality of failing to bring about sub- 75 all oi the last traces of moisture from the feed,

resulting in the utilization of a feed approaching absolute dryness, greatly increases the rate of reaction of the hydrogen halide with the olefin in the fractionatlng zone over that prevailing when traces of moisture, ranging for example 5 from about 20 to about 700 parts per million by weight of the total charge, are present. The increase in the rate of interaction of hydrogen chloride and prop lene-under fractionating conmillion by weight.

to the fractionating zone. The moisture content of the charge to the fractionating zone is Preferably maintained in the range of from about 20 to about 700, and still more preferably in the range of from about 20 to about 200 parts per Maintenance of the water content within the preferred limits in the preferred method of effecting the fractionation may be obtained by judicious control of the charge ditions resulting from removal of thelast traces dehydrating means employed and/or by the addiof moisture from the charge is illustrated by the following example:

Example IV The effect of moisture on the hydrochlorination 5 the propylene is determined by analysis of propylene removed from the test vessel after charging. Hydrogen chloride, the moisture content of which is determined, is thereupon introduced into tion of water to the charge prior to its passage into the fractionatlng zone. I

The inclusion of such controlled quantity of water in the charge in combination with the use of a fractionating zone wherein the surfaces in contact with material undergoing fractionation consist essentially only of nickel, therefore provide a means of effecting the desired hydrogen halide separation with an unusually high degree full with liquid propylene. Moisture content of of efliciency.

The following example is illustrative of the substantial advantages which may be obtained in practical scale operation of the process by the maintenance of traces of moisture in the charge the vessel and the vessel scaled. After a recorded to the fractionating zone.

period of time the production rate of isopropyl chloride is determined. The operation is repeated in seven additional operations. In three tests where moisture contents of less than 20 parts per Example V A mixture of propylene and hydrogen chloride containing 15 mol per cent of hydrogen chloride,

million were attained (operations Nos. 1, 2, and 6), and w r ranging m 7 t0 2 p r y wei ht drying of the propylene charge is accomplished in liquid phase with phosphorus pentoxide. In operations Nos. 1 and 6, the limit of. sensitivity of the analytical method (4 to 8 P. P. M.) is

of the total feed, is fractionated in a steel column of 3.5 ft. diameter containing 30 steel bubble cap decks. A feed rate of 82 pound-mols per hour and a column pressure of 220 pounds per square reached; 1. e., no moisture can be detected'with inch auge are e p oyed. he result in terms certainty. The water content of the propylene charge, the concentration of the hydrogen chloride, the duration of the test in hours, and the rate of isopropyl chloride production in terms of of isopropyl chloride production and hydrogen. chloride conversion within the column are indicated in column A of the following table. The operation is repeated under substantially identilb of isopropyl hl i produced per 1000 sq fl; 40 cal conditions with the exception that a nickelclad column affording the contact of only a nickel surface with the material undergoing fractionation is employed. The results obtained with the water-Com 150mm,] nickel-clad column are indicated in column B Operation tent of 110100110. Dilzration, Chloride of the following table. The operations in the ?*i fii?' percent ours ggfi steel and nickel-clad column are again repeated under substantially identical conditions but with 7 20 46 the exception that a substantially anhydrous feed is 2g f: (i. e. containing less than 20 P. P. M. of water) 38 51 18 15 50 to' each fractionator are employed. Results ob- 76 8 24 16 tained in the steel and nickel-clad column under 4 17 s1 19 30 19 11 34) substantially anhydrous conditions are indicated 53 24 17 in columns C and D, respectively of the following table:

A B o D Charge Wet Wct Anhydrous Anhydrous. Column Surface Steel. Nickel; Steel Nickel. Rate (at 150 ropyl Chloride Production in lbs. per 1,000 130 6.5.... 390 19.5.

sq. Bl Olll. Isopropy Chloride Production, lbs. per day 4,680 235 14,040 705. Hydrogen Chloride Conversiompereent 3 0.15.. 10 0.5.

As'evidenced by the foregoing example the re- As stressed in the foregoing detailed descriplion. In the preferred method of execution of the invention traces of moisture in excess of about 20 parts per million are maintained in the charge tion thereof, the invention is applied with particular advantage to theseparation of a hydrogen halide such as hydrogen chloride from admixture with a normally gaseous olefinic hydrocarbon such as, for example, ethylene, propylene and the butylenes. It is to be understood, however, that the invention is in no wise limited in its application to the separation of a hydrogen chloride from normally gaseous olefins but may be applied to the separation of hydrogen chloride from other olefinic hydrocarbons which do not tion is furthermore not limited to the resolution of olefin-containing mixtures comprising hydrogen chloride as the hydrogen halide but may be applied to the separation of mixtures comprising the olefinic hydrocarbon in admixture with another hydrogen halide such as, for example, hydrogen bromide or hydrogen fluoride.

The fractionating zone employed in the execution of the invention may comprise any of the many types of fractionators such as, for example, columns or stills equipped with suitable bubble cap plates, baflles, packing, or the like, substantially all surfaces of which coming into contact with the mixture undergoing fractionation consist essentially of nickel.

The olefin and hydrogen halide containing charge is introduced into the fractionating zone substantially in the liquid phase, The pressure maintained within the fractionating zone will of course vary to some dgree with the composition of the charge and specific type of fractionator and operating methods employed. The pressure within the column is, however, maintained sufilciently high to assure the production of an overhead product consisting essentially of hydrogen halide.

We claim as our invention:

1. In a process for the separation of hydrogen chloride in a state of high purity from a mixture containing said hydrogen chloride in admixture with an olefin' by fractionating said mixture at an elevated pressure, the improvement which comprises effecting said fractionation in a fractionating zone in which substantially all surfaces contacting said mixture undergoing fractionation are essentially only of nickel thereby effecting said fractionation in the absence of any substantial interaction of said hydrogen chloride and said olefin.

2. In a process for the separation of hydrogen chloride in a state of high purity from a mixture containing said hydrogen chloride in admixture with a normally gaseous olefin by fractionating said mixture at an elevated pressure, the improvement which comprises effecting said fractionation in a fractionating zone in which substantially all surfaces contacting said mixture undergoing fractionation are essentially only of nickel thereby efi'ecting said fractionation in the absence of any substantial interaction of said hydrogen chloride and said olefin.

3. In a process for the separation of hydrogen chloride in a state of high purity from a mixture containing said hydrogen chloride in admixture with propylene by fractionating said mixture at an elevated pressure, the improvement which comprises effecting said fractionation in a fractionating zone in which substantially all surfaces contactingsaid mixture undergoing fractionation are essentially only of nickel thereby effecting said fractionation in the absence of any substantial interaction of said hydrogen chloride and said propylene.

4. In a process for the separation of hydrogen chloride in a state of high purity from a mixture containing said hydrogen chloride in admixture with an olefin by fractionating said mixture at an elevated pressure, the improvement which comprises effecting said fractionation in a fractionating zone in which substantially all surfaces contacting said mixture undergoing fractionation are essentially only of nickel, and maintaining traces of moisture in excess of about 20 parts per million in said mixture charged to said fractionating zone, thereby effecting said fractionation in the absence of any substantial interaction of said hydrogen chloride and said olefin.

5. In a process for the separation of hydrogen chloride in a state of high purity from a mixture containing said hydrogen chloride in admixture with a normally gaseous olefin by fractionating said mixture at an elevated pressure, the improvement which comprises eflecting said fractionation in a fractionating zone in which substantially all surfaces contacting said mixture undergoing fractionation are essentially only of nickel, and maintaining a water content of from about 20 to about 200 parts per million in said mixture charged to said fractionating zone, thereby effecting said fractionation in the absence of any substantial interaction of said hydrogen chloride and said olefin.

6. In a process for the separation of a hydrogen chloride in a state of high purity from a mixture containing said hydrogen chloride in admixture with a normally gaseous olefin by fractionating said mixture at an elevated pressure, the improvement which comprises effecting said fractionation in a fractionatingzone in which substantially all surfaces contacting said mixture undergoing fractionation are essentially only of nickel, and maintaining a water content of from about 20 to about 700 parts per million in said mixture charged to said fractionating zone, thereby effecting said fractionation in the absence of any substantial interaction of said hydrogen chloride and said olefin.

7. In a process for the separation of a hydrogen chloride in a state of high purity from a mixture containing said hydrogen chloride in admixture with a propylene by fractionating said mixture at an elevated pressure, the improvement which comprises effecting said fractionation in a fractionating zone in which substantially all surfaces contacting said mixture undergoing fractionation are essentially only of nickel, and maintaining a water content of from about 20 to about 700 parts per million in said mixture charged to said fractionating zone, thereby effecting said fractionation in the absence of any substantial interaction of said hydrogen chloride and said propylene.

8. In a process for separating hydrogen chloride from a mixture containing said hydrogen chloride in admixture with normally gaseous olefins consisting essentially of propylene by fractionating said mixture at an elevated pressure,

the improvement which comprises eifecting said fractionation in a fractionating zone in which substantially all surfaces contacting said mixture undergoing fractionation are essentially only of nickel, and maintaining traces of moisture in excess of about 20 parts per million in said mixture charged to said fractionating zone, thereby effecting said fractionation in the absence of any substantial interaction of said hydrogen halide and said olefin.

Name Date Baehr et a1. Jan. 7, 1941 Number 2,227,953 

